In the prior art it is known that the breaking resistance qualities of a moldable rigid thermoplastic with respect to an impact are enhanced by the addition of an elastomeric component to the thermoplastic. Typically, the elastomeric component is introduced into the thermoplastic by blending a proportion of an elastomer containing "particle" with a thermoplastic resin. Examples of such types of additive particles and blends are described, for example, in the specifications of U.S. patents of Griffin et al., U.S. Pat. No. 3,450,796, issued on June 17, 1969 entitled "Production of Thermoplastic Polymeric Materials;" Owens, U.S. Pat. No. 3,793,402 issued Feb. 19, 1974 entitled "Low Haze Impact Resistant Composition Containing A Multi-Stage Sequentially Produced Polymer," and U.S. Pat. Nos. 3,808,180 and 3,843,753 respectively issued Apr. 30, 1974 and Oct. 22, 1974, both entitled "Composite Interpolymer and Low Haze Impact Resistant Thermoplastic Compositions Thereof;" and Hofmann, U.S. Pat. No. 4,180,529, issued Dec. 25, 1979 entitled "Acrylic Multistage Graft Copolymer Products and Processes."
Such particulate additives are produced by successive and ordered emulsion polymerizations which usually provide alternating elastomeric and rigid thermoplastic components, beginning with a first "core" or "seed" particle. The art, such as that identified above, describes various ordered arrangements of elastomeric and thermoplastic "stages" in such particles. In this manner, a layered particle is produced which is then blended with a principal proportion of matrix thermoplastic, the impact properties of which it is desired to enhance. Typically, the outer shell of such particles is a thermoplastic, which is compatible for blending with the matrix thermoplastic. Further, such layered particles have also included various co-polymeric cross-linking and graft-linking components in the elastomeric and thermoplastic stages of the particle.
Such layered particles conventionally require precise process control during the emulsion polymerizations to achieve optimum results. Various difficulties may be encountered in terms of control over the formulation and the time and temperature cycles required for the successive emulsion polymerizations.
It has heretofore been a principle in the art that the composition of an individual layer in such a particle cannot be characterized apart from the properties of the particle as a whole. In seeking to achieve useful varieties of such particles, the art has varied the monomer and co-monomer formulations which produce the successively polymerized stages in layered particles, and in so doing, has generally alternated elastomeric and thermoplastic layers to provide a particle for blending which contains the predetermined quantity of elastomer which is necessary to be introduced into and blended with the matrix polymer to produce the required degree of impact resistance.